[optimizing] Improve x86, x86_64 code
Tweak the generated code to allow more use of constants and other small
changes
- Use test vs. compare to 0
- EmitMove of 0.0 should use xorps
- VisitCompare kPrimLong can use constants
- cmp/add/sub/mul on x86_64 can use constants if in int32_t range
- long bit operations on x86 examine long constant high/low to optimize
- Use 3 operand imulq if constant is in int32_t range
Change-Id: I2dd4010fdffa129fe00905b0020590fe95f3f926
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>